Dry powder inhalers are known, such as TECHNOHALER, being developed by Innovata Biomed in the UK. Such a device is described in International Patent Application No. WO 93/16748 (PCT/GB93/00335). WO '748 describes an inhaler which comprises a disc like magazine having a plurality of medicament carrying receptacles around its periphery. Each receptacle comprises a spool housed in a spool carrier. Each spool has a flange at each end which form a tight slidable fit within the body of the spool carrier. The space left between the body of the spool and the spool carrier is filled with an appropriate medicament.
The known TECHNOHALER is provided with suitable indexing means, including a push button and a ratchet mechanism which engages with the upper surface of the disc. Depression of the push button urges a push rod to push the spool, which is adjacent the inhalation passage of the inhaler, downwards and almost fully out of the spool carrier, and into the inhalation passage. As the spool is pushed into the inhalation passage, it carries with it the measured quantity of medicament which it has been used to contain inside the magazine. The user can then inhale through the mouthpiece so as to take up the drug now released into the inhalation passage. The upper flange of the spool remains, however, held by the lower part of the receptacle. When the user then releases push button, the ratchet mechanism causes the disc to rotate by one step so that the next receptacle is brought into register with the inhalation passage. The inhaler is thus reset and ready for delivery of another dose of drug. The “empty” spool not having been pushed fully out of the first receptacle, continues to move round with the first receptacle, supported by the lower guide.
In the inhaler of the prior art whilst the spool magazine lies essentially in the same plane as the as the mouthpiece of the inhaler, the push rod acts on a spool in a perpendicular plane.